Antimicrobial polymers polymeric biocides

Antimicrobial polymers have been classified in three different major groups. There are biocide-releasing polymers, polymeric biocides, and biocidal polymers (Figure 15.2). 

The use of polymeric ammonium salts and a sulfonic acid salt of sodium is an easy and efficient way of coating fabrics furthermore, employing the layer-by-layer (LbL) deposition technique can broaden the application of N-halamine biocides in other polar substances for use as antimicrobial coatings. Branched PEI, polypropylene (PP) and styrene maleic anhydride copolymers are a very good coating for food packaging materials, possibly due to the presence of both cationic- and N-halamine-forming structures. N-halamine cationic antimicrobial polymers based on (acrylamidopropyl)trimethylammonium chloride, PDDA chloride and poly(2-acrylamido-2-methylpropane sulfonic acid sodium salt) have been synthesised and coated onto cotton fabrics via an LbL deposition technique. 

In general, biocide-releasing polymers have no influence over their intrinsic antimicrobial activity. The polymers are simply acting as carriers for biocides or antibiotics. The biocidal molecules, which are incorporated in the polymer matrix and/or tethered to the polymer backbone, are released. One of the major advantages of these systems is that the release of the embedded antimicrobial active substances is controlled by the used polymeric system. Therefore, the rates of release are adjustable and polymers can release the biocides very close to the cell, which makes them efficient. However, the polymers still release biocides into the environment and will eventually become inactive. Polymeric biocides contain biocidal repeating units. Such macromolecules often show the same mode of action as their repeating units with somewhat lower activity, due to the steric hindrance caused by the polymeric backbone. Biocidal polymers distinguish themselves by the fact that they act as a whole molecule. Further, biocidal polymers have been found to show a lower tendency to build up bacterial resistance. ... 

Figure 15.2 General working principles of antimicrobial polymers (a) biocidereleasing polymers, (b) polymeric biocides, and (c) biocidal polymers.

Biocidal polymers are considered to be the next generation of antibiotics which can be effectively used against microbial infections. The antimicrobial activities of silver-bearing functionalised polymers and L-lactide polymeric NP are an important aspect in the prevention of bacterial skin and urinary tract infections. Biologically derived compounds, such as bacteriocins, phytochemicals and enzymes, can be used in antimicrobial food packaging. 

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